Hi Morimoto-san,
On Thu, May 27, 2021 at 12:06 AM Kuninori Morimoto
<kuninori.morimoto.gx@xxxxxxxxxxx> wrote:
> > Oh right, I missed the static clk_hw pointer.
> > What if you unload the snd-soc-rcar.ko module?
>
> Hmm.. indeed.
> It needs something..
> Thank you for poining it.
>
> > #define for_each_rsnd_clk(pos, adg, i) \
> > for (i = 0; (pos) = adg->clk[i], i < CLKMAX; i++) \
> > if (pos) { \
> > continue; \
> > } else
>
> Wow!! I didn't know this technique.
> Indeed it can use NULL pointer.
>
> But, I want to avoid "if (pos) else" code as much as possible,
> and keep simple code.
> It can handle all clk case without thinking it if it has null_clk.
>
> Why you don't want null_clk ??
It adds a dummy object, which needs to be cleaned up. Basically you
are trading a simple NULL pointer check for a zero clock rate check
deeper inside the driver, with the additional burden of needing to
take care of the dummy clock's life cycle.
Note that most clk_*() calls happily operate on a NULL pointer, and
just return success. This includes clk_get_rate(), which returns
a zero rate.
Mark might have a different view, though, due to his experience with
dummy regulators?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
